Tascam 38 22-2 22-4 and others external panel fascia cosmetic guide roller cover rings Size:21mm it was from an A3440

it was from an A3440 but I am guessing this is a common part in several machines of that era

The caps have a different longer thread  to them the TSR8 cap is a straighter side but fits the 38 and vice versa e 38 cap has a bevel the TSR8 is straight a photo is included so you can see the difference

This is the export model s 220 230 240v

Had some more come in with a 10k log dual

Tascam 38 22-2 22-4 and others external panel fascia cosmetic guide roller cover rings Size:21mm it was from an A3440These rings were more for cosmetic reasons and were used on many of the Tascam tape recorders I was asked a few times about these so have put a few here, they may have a slight mark on the bottom where they have to be lifted off but the mark normally sits in the recessed section, its an odd spare but seems people get theirs scratched etc. I have the larger one thats seen on the 32 34 38 and also a smaller one thats used around the capstan on some